Fuel cell assemblies employing proton exchange membranes are well known. Such assemblies typically comprise a stack of fuel cell modules, each module having an anode and a cathode separated by a catalytic proton exchange membrane, and the modules in the stack being connected in series electrically to provide a desired voltage output. Fuel in the form of hydrogen, or hydrogen-containing mixtures such as “reformed” hydrocarbons, is flowed through a first set of reaction channels formed in the anode surface adjacent a first side of the membrane. Oxygen, typically in the form of air, is flowed through a second set of reaction channels formed in the cathode surface adjacent the opposite side of the membrane. Hydrogen is catalytically oxidized at the anode-membrane interface. The resulting proton, H+, migrates through the membrane to the cathode-membrane interface where it combines with ionic oxygen to form water. Electrons flow from the anode through a load to the cathode, doing electrical work in the load.
Protons migrate only in those areas of the fuel cell in which the anode and cathode reaction channels are directly opposed across the membrane. Misalignment between anode and cathode channels results in some portion of the anode channels unopposed by cathode channels, and correspondingly, an equal area of the cathode channels unopposed by anode channels. Thus, the effective area of membrane for migration is reduced, and so, proportionally, is the electrical output of the fuel cell.
In the prior art, anodes and cathodes typically are aligned visually during assembly by aligning outer edges, which edges are not necessarily of uniform distance from the reactive areas on the anodes and cathodes. What is needed is a method and apparatus for assuring that the reactive areas on the anodes and cathodes are aligned fully and automatically during assembly of a fuel cell.
It is a principal object of the present invention to provide an improved method and apparatus for fully and automatically aligning an anode and a cathode during formation of a bipolar plate.
It is a further object of the invention to provide an improved method and apparatus for fully and automatically aligning a plurality of bipolar plates in assembling a fuel cell stack.